the swiftech 4870 block will work for you...I have 2 of the same cards, and am travelling dow nte smae path as you...these cards NEED water. No such thing as a decent air cooler, that doesn't take up three slots, which is no good with me having more than one card.

Did you mean this block? In the chart at the bottom of the page it specifically says my card is not compatible with the mosfet cooling, but is compatible with the ram and gpu core. How much of a load is from the mosfets? Would a small heatsinks be fine on the mosfets?

The only reason I would cool my cpu is to make more room in the case for a rad behind the cpu socket.

As far as a single 120.1 rad, I'm not going for record overclocking so if my temps under load hit 50-60C I could handle it. What sort of load temps could I expect in worst case scenario?

there is already a heatsink on the mosfets, so simply remove the mosfet attachment on the block, and put some quiet 40mm fans over the 'fets. I might even see if I cannot intergrate the heatpipe into the stock mosfet heatsink...

Take a look at the Sapphire Toxic 4870x2...two of the same cores on a single 120mm rad, plus cpu block. With aircooling the vga's power area, as well as no cpu, it should be ok, but if possible, I'd suggest a 2x120mm rad for when summer hits.